The characteristics of petroleum crudes is typically dependent on the geographical location of the reservoir and its geological origin and extent of biodegradation. While it is more desirable to produce lighter, lower viscous, low acidity sweet crudes, such crudes are becoming harder and harder to find. Many crudes on the market today are heavy and sour crudes having high acidity and high viscosity and have poor flow properties making them difficult to recover from underground reservoirs, difficult to transport via pipeline. Also, in the refinery, the residuum resulting from such crudes suffers from the same flow problems, as well as having poor injection properties that can plug process equipment or render less effective the processing of such crudes.
The conventional approach to crude upgrading has focused on viscosity reduction. Viscosity reduction is important in the production, transportation and refining operations of crude oil. Transporters and refiners of heavy crude oil have developed different techniques to reduce the viscosity of heavy crude oils to improve its pumpability. Commonly practiced methods include diluting the crude oil with gas condensate and emulsification with caustic and water. Thermally treating crude oil to reduce its viscosity is also well known in the art. Thermal techniques for visbreaking and hydro-visbreaking (visbreaking with hydrogen addition) are practiced commercially. The prior art in the area of thermal treatment or additive enhanced visbreaking of hydrocarbons teach methods for improving the quality, or reducing the viscosity, of crude oils, crude oil distillates or residuum by several different methods. For example, several references teach the use of additives such as the use of free radical initiators (U.S. Pat. No. 4,298,455), thiol compounds and aromatic hydrogen donors (EP 175511), free radical acceptors (U.S. Pat. No. 3,707,459), and hydrogen donor solvent (U.S. Pat. No. 4,592,830). Other art teaches the use of specific catalysts such as low acidity zeolite catalysts (U.S. Pat. No. 4,411,770) and molybdenum catalysts, ammonium sulfide and water (U.S. Pat. No. 4,659,453). Other references teach upgrading of petroleum resids and heavy oils (Murray R. Gray, Marcel Dekker, 1994, pp. 239-243) and thermal decomposition of naphthenic acids (U.S. Pat. No. 5,820,750).
It is taught in U.S. Patent Application Number 20040035749 that the flow properties of crude petroleum having an API gravity varying from about 6 to 12 are improved by heating the crude petroleum to a temperature of about 35° C. to 200° C. and, in the presence of a suitable viscosity reducing additive, shearing the heated crude petroleum with a high shearing force sufficient to reduce the viscosity of the crude petroleum to a range of about 250 centipoise (cP) to about 1000 cP. Suitable viscosity reducing additives include gasoline, naphtha, butanol, petroleum ether, diesel fuel, citrus oil based cleansers and degreasers, and mixtures thereof.
Also, U.S. Patent Application Number 20030132139, which is incorporated herein by reference, teaches decreasing the viscosity of crude oils and residuum by utilizing a combination of acid and sonic treatment. Each one alone does not substantially decrease viscosity and only when energy, in this case in the form of sonic energy is used in combination with an acid will a substantial decrease in viscosity result.
While there is much art in reducing viscosity to enhance the flow properties of crude oils it has generally been overlooked that crude oils are also viscoelastic fluids and thus, many of the heavy crude oils, those with high viscosities, also have relatively high elasticity. The high elasticity heavy oils have adverse impact on flow and particularly during injection of the heavy oil in process vessels. The most commonly employed technology for upgrading heavy oil is coking. Viscoelastic oils present unique challenges in feed injection to cokers due to the formation of so-called “necks” or filaments during feed injection. Improvements in feed injection by elimination of filaments or necks can improve heavy oil coking efficiency. Therefore, there remains a need in the art to treat a crude oil with a reagent that can desirably affect the elastic properties of crude oils.